<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <script src="../../vue.js"></script>
</head>

<body>
  <div id="app">
    <!-- <ul>
      <li v-for='c in citys'>{{c}}</li>
    </ul> -->
    {{users.age}}
  </div>

</body>
<script>

  var vm = new Vue({
    el: '#app',
    data: {
      citys: ["北京", "天津", "上海"],
      users: {
        name: 'changyi'
      }
    }
  })

  vm.$set(vm.users, 'age', 17)



</script>

</html>